The substructure that ensures the existence of the superstructure of the modernized heritage structures is a component that has heritage value inseparable from the superstructure. This paper will examine the foundation structures of the Nirayama Reverberation Furnace, Dry Docks, Tomioka Silk Mill, Shirakabe Barrack, Tokyo Bay Fortress, and Obaradai Redoubt according to the year of completion. Then, as an example of historical buildings and their stabilization, it will take the Leaning Tower of Pisa and examine the way of restoration of heritage structure. The components and characteristics of the foundation structures that secure these heritage structures will be clarified, and the evaluation and restoration of heritage structures that should be preserved for future generations will be shown.

The strength and deformation characteristics of construction materials for civil engineering historic sites constructed after the end of the Edo period were analyzed from the rebound hammer test RHT, unconfined compression test, and split tensile strength test. The measurement materials were stone (9 facilities), concrete (13 facilities), and brick (6 facilities) from 171 years ago. In addition to masonry walls and bricks including joints, the strength and deformation characteristics of bricks, stones, and concrete were related to dry density and unconfined compressive strength were interpreted in a unified manner. In addition, a regression equation was shown that unconfined compressive strength can be estimated from the strength of RHT. This regression equation was well explained not only for civil engineering historical sites using bricks, concrete, and stone, but also for today’s concrete. The International Organization for Standardization and the International Council on Monuments and Sites have also shown the actual conditions of the strength and deformation characteristics of the components of heritage structures.

A mechanically stabilized gabion wall is constructed with gabions as wall facing and geosynthetics as reinforcements. The gabion unit is composed of a gabion box and a steel mesh tail extending from the bottom of the gabions. According to the Geosynthetics Manual¹⁾, sufficient connection strength between the wall facing and the geosynthetics is required in a mechanically stabilized earth wall. For our mechanically stabilized gabion wall, the gabion units filled with rocks and the backfill above the extended steel mesh are being considered as the wall facing. In this research, the friction between the wall facing and the geosynthetics is considered as the connection strength, which was calculated from the lab experiment results. Using the calculated connection strength, we verified that there were more pullout strengths than the required tension for a mechanically stabilized gabion wall with a height of 15 m and gradients of 1:0.1 to 1:0.5. In conclusion, the mechanically stabilized gabion wall is evaluated to be a reliable structure of the gabion units and the geosynthetics.

To estimate the lifetime of an immobilizer used for countermeasures for disposing of excavated rocks containing hazardous trace elements such as arsenic, the appropriate method for evaluating the solubility of the immobilizer is required. In our previous study, the solubility-limiting solid phase that governs the solubility of the immobilizer, was assumed based on the saturation index (SI) of each mineral calculated using water chemistry of the leachate obtained by batch immobilization experiments. In this study, the formation of the solubility-limiting solid phases was confirmed by electron microscopic (EPMA) observation and elemental mapping analysis by using the residues of batch immobilization experiments. The results observed by EPMA showed that brucite as a solubility-limiting solid phase of Mg-bearing immobilizers, formed surrounding magnesium oxide. In case of using Ca-bearing immobilizers containing Mg, Mg ion was sorbed on calcite and dolomite-like secondary mineral was formed, which could behave as the solubility-limiting solid phase. These results indicate that the prediction of the solubility-limiting solid phase by SI based on the results of batch immobilization experiments was also consistent with and supported by the results of microscopic observations and elemental mapping analysis of the solid phase.

In landslide areas, lateral boring and catchment wells are installed to remove groundwater. The water catchment pipe inserted in this lateral boring often becomes clogged due to blockages over time. One of the factors contributing to these blockages could be the sols and gels formed in the biofilms that have developed over many years in hard-to-clean areas such as the outer walls of the collection pipes. In this study, a system was developed to clean these using micro-nano bubbles (fine bubbles), and experiments were conducted in multiple collection wells. This system was shown to be effective even for catchment pipes with blocked holes by increasing the concentration of micro/nano bubbles in catchment wells where biofilms have matured and their soundness has decreased. In addition, a method was proposed to objectively evaluate the cleaning effect based on the soundness (level) obtained from the flow rate before and after cleaning.

When a residential land is hit by a major earthquake, the concerns of home-owners are whether the residential land has seriously damaged and whether they can continue to live safely in the future. One method for estimating the degree of ground damage is to investigate changes in the dominant frequency of the ground. So far, the degree of ground damage has been estimated by array observation networks using multiple seismometers, and by comparing seismic motion records between the bedrock and the ground surface. However, it is difficult to install multiple seismometers in a house. Therefore, in this study, a method to quantify the degree of decrease in stiffness of residential ground was investigated using the acceleration record of a single seismometer installed on the ground surface. The running spectrum was calculated from the acceleration record divided every 6 seconds, and the degree of decrease in stiffness was expressed by quantifying the amount of movement of the dominant frequency during the initial microtremor and other time periods. Comparing with the damage situation of the 3 observation points in the 2011 off the Pacific coast of Tohoku Earthquake, the result of the proposed method is consistent with the damage situation of the 3 observation points.

In this study, the method for determining the schematic shear strength of embankment materials was examined for use in identifying sections of existing embankments that require aseismic reinforcement. The shear strength used for the aseismic diagnosis of existing embankment was determined considering soil type. For clayey soil, uniform values were proposed based on the difference between the mean values and standard deviations of strength parameters obtained from the triaxial compression test results. For sandy soil, the estimation method of strength parameters was proposed based on the estimated internal friction angle, which considered the grain size characteristics and the density, and the cohesion, which considered unsaturated strength characteristics. The circular-slip stability analysis using the strength parameter of the embankment materials was conducted to clarify the scope of application of the proposed method. The results show that the stability of the embankment is satisfied up to a height of about 4.5 m for clayey soil embankments and up to a height of about 6.0 m for the sandy soil embankments with a good grain size distribution and high density. The results revealed a scope of application consistent with the actual seismic performance of the existing embankments.

In this paper, in addition to the relationship between the heating temperature and the mass ratio in the heating tests conducted on gypsum so far, the thermal behavior of gypsum related to change in form was discussed again based on the relationship between the heating temperature and the mass error, and by rearranging the relationship between the heating temperature and the mass, the relationship between the heating temperature (the oven-drying temperature) and the water content was investigated in detail. Further, the water content tests were conducted on reagent gypsum and recycled gypsum using JIS method (110 ℃). The results obtained showed that when reagent gypsum and recycled gypsum without adding water were oven dried at 110 ℃ for 24 hours using JIS method, the water content obtained was that of gypsum that was converted from gypsum dihydrate to gypsum hemihydrate or gypsum anhydrate, and from gypsum hemihydrate to gypsum anhydrate, and it was found that the apparent water content was larger than the true water content.

Generally, a land developed by the cutting and embanking work consists of the business area and the slope area, both of which are constructed by compacting the embankment soil to a certain degree or higher, but the slope area also requires the strength necessary for slope stability. When the ground to be cut is composed of sedimentary rocks such as mud stone, the cementation degree, the weathering degree, and so on varies depending on the environment and the elapsed years after depositing, the embankment soil showing various compaction and strength characteristics. For this reason, even if the embankment ground is constructed with the required compaction degree, the strength parameters of the slope area may not satisfy the strength parameter in design. This paper reports the results of a compaction and strength control method that considers only the natural water content w_n and its applicability to a cutting and embanking construction project on soft mudstone ground, where the compaction and strength properties of embankment soils differ depending on the cutting position in the ground.

We investigated the frost-susceptibility and freeze–thaw resistance of foam glass lightweight gravel, a recycled material made from waste glass, for use in cold regions. The lightweight non-frost-susceptible material used in the experiments was confirmed to have sufficient freeze–thaw resistance. An examination of its basic properties revealed that the particles contained many closed voids, and thermal conductivity values were about 1/25th of those for general crushed stone, indicating high thermal insulation performance. Based on these characteristics, we proposed using foam glass lightweight gravel as a fill material for road frost blankets and for slope protection gabions, and we demonstrated its effectiveness through heat transfer analysis and field tests.